Field of the Invention
The invention relates to a method, a measuring device and a data carrier for determining the density of a fluid.
For the accurate determination of the density of a fluid with a flexural resonator, stable environmental conditions and a defined operating state of the flexural resonator are necessary. Otherwise, the measurement can be influenced detrimentally by disruptive environmental influences, such as air pressure, atmospheric humidity, temperature, dust particles, chemical vapors, shocks and/or vibrations, as far as damage to or destruction of the flexural resonator in the event of long-term presence of the disruptive influence.
In particular for the highly accurate determination of the density of liquids, a stable temperature of the measuring cell is vital. In many applications, the measuring temperature lies below the ambient temperature. Typical measuring temperatures are 15° C., 20° C., 60° C. For special applications, the temperature also often lies below 10° C. In particular, the operation of a measuring cell in a moist, warm environment constitutes a challenge, since the operating state can lead to the formation of condensation in the measuring cell, which can lead to destruction of the latter.
In the event of many measuring errors and of damage to devices in the field, the causes and if need be the question of liability cannot be clarified, since the triggering and actual conditions cannot be reconstructed.
It is known to encapsulate measuring cells in a dust-tight and gas-tight manner for process applications and therefore to minimize the influence of the environmental conditions. It is also known to equip the housing of measuring cells with flexural resonators with dry air purging or to integrate drying cartridges into the housing. Measuring cells constructed to be gas-tight are expensive and can be implemented technically only with very great difficulty; most of the time only specific influences can be ruled out with such solutions. For instance, dry air purging or the use of drying cartridges is operationally reliable only to a limited extent, primarily with regard to the errors by the user. If the dry air purging is not connected correctly, condensation can form in the housing interior, which can lead to destruction of the measuring cell.